1) Field of the Invention
The present invention relates to an information processing system. In particular, the present invention relates to a distributed processing system realizing an N-tier client-server environment. The present invention also relates to a method for updating a program component loaded in a server in an N-tier client-server environment.
2) Description of the Related Art
Recently, communication networks are required to have various functions. In order to provide various services to customers, manage operations, and maintain such communication networks, it is necessary to timely update versions of programs in the communication networks. In particular, in backbone networks, it is impossible to stop the entire system or a process executed in the system. Therefore, the programs must be dynamically replaced during regular operations of the communication networks.
According to a conventional dynamic program replacement technique, a new version of a program is queued, and then replaces an old version of the program. Thereafter, communication is restarted. According to another conventional dynamic program replacement technique, one or more requests for execution of an old version of a program are cancelled, and then the old version of the program is replaced with a new version of the program. According to the above conventional techniques, it is not necessary to stop the entire process or the entire system. However, transaction processing is temporarily blocked or stopped.
On the other hand, distributed processing systems are widely used in the communication networks. The so-called client-server system is a typical example of the distributed processing system. Currently, the so-called N-tier client-server system is considered to be a next-generation client-server system, and is under development. In the N-tier client-server system, more than one tier is formed above a client tier.
However, the conventional dynamic program replacement techniques are proposed for merely replacing an old version of a program with a new version of the program. Therefore, the conventional dynamic program replacement techniques cannot achieve dynamic replacement of a plurality of old versions of a plurality of software components distributed over a plurality of computers forming an N-tier client-server system, with new versions of the plurality of software components, so as to maintain synchronization between the versions of the programs in the plurality of computers during the replacement.